A mixed powder for foamed aluminum, a foamed aluminum composite material, and a method for producing the same

Abstract

The application provides a mixed powder for foamed aluminum, a foamed aluminum composite material and a preparation method thereof, the mixed powder comprising a base material, a foaming agent and a brazing agent; the base material comprises aluminum elements, silicon elements and copper elements; the copper elements exist in the form of copper powder; the difference between the solidus temperature of the brazing agent and the hot rolling temperature is-30 DEG C to 30 DEG C, and the mass percentage of the brazing agent is greater than or equal to 0.2wt% based on the mixed powder. For the foamed aluminum alloy system with Cu as a secondary main alloy element, the application can directly foam without diffusion annealing, and uniform and small pores are obtained, so the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of foamed aluminum technology, and in particular to a mixed powder for foamed aluminum, a foamed aluminum composite material, and a method for preparing the same. Background Technology

[0002] Closed-cell aluminum foam is a lightweight, porous metallic material with low density, high specific strength, excellent energy absorption and shock absorption, sound and heat insulation, electromagnetic shielding, and corrosion resistance. Its closed-cell structure gives it good cushioning performance, effectively absorbing impact energy, while also exhibiting outstanding thermal insulation properties with low thermal conductivity and significant sound insulation effects. Combining the strength of metals with the lightweight advantages of porous materials, closed-cell aluminum foam is widely used in aerospace (e.g., lightweight structural components), automotive industry (collision energy absorption components), construction (sound and heat insulation materials), rail transportation (vibration and noise reduction), and electronic equipment (electromagnetic shielding), making it a high-performance, functionally and structurally integrated material.

[0003] The powder metallurgy method for preparing closed-cell aluminum foam has significant advantages: This method involves uniformly mixing metal powder with a foaming agent, followed by pressing, sintering, and in-situ foaming. The process is highly controllable, allowing for precise control of porosity and pore size distribution. The resulting closed-cell structure is uniform and stable, with dense pore walls and few defects. The material exhibits excellent mechanical properties (such as specific strength and energy absorption efficiency) and functional characteristics (such as sound insulation, heat insulation, and electromagnetic shielding). It does not require complex molds or high-pressure equipment, making it suitable for small-batch customized production. It is also compatible with various aluminum alloy systems (such as Al-Si and Al-Mg alloys), and has broad application prospects in fields such as automotive lightweighting, aerospace cushioning components, and building sound-absorbing materials.

[0004] Currently, the preparation of foaming precursors directly using pure metal powders results in insufficient mixing of alloying elements, failure to form an alloy, failure to lower the melting point to the alloy's melting point, and uneven melting. This is detrimental to the subsequent foaming process. CN111842898B addresses this issue with a powder metallurgy diffusion method for preparing aluminum foam and the resulting aluminum foam and sandwich aluminum foam boards, belonging to the field of non-ferrous metal technology. The specific steps of the method are as follows: aluminum powder, silicon powder, and copper powder are mixed to replace traditional aluminum alloy powder, then mixed with a foaming agent and a thickener. After cold pressing, hot rolling, or hot extrusion, a diffusion annealing step is performed, causing the aluminum, silicon, and copper in the material to become alloy phases while eliminating defects such as cracks and pores. Subsequently, heated foaming is performed to prepare aluminum foam, or it is composite hot-rolled with pure metal sheets before foaming to prepare sandwich aluminum foam boards. However, this preparation method requires a long diffusion annealing process, extending the production cycle and increasing costs and energy consumption.

[0005] Therefore, there is a need to develop new aluminum foam products and preparation methods. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a mixed powder for foamed aluminum, a foamed aluminum composite material, and a method for preparing the same. For foamed aluminum alloy systems with Cu as the secondary alloying element, direct foaming can be achieved without diffusion annealing, resulting in uniform and fine pores.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a mixed powder for foamed aluminum, the mixed powder comprising a matrix raw material, a foaming agent, and a flux. The matrix raw material comprises aluminum, silicon, and copper. The copper exists in the form of copper powder. The difference between the solidus temperature and the hot rolling temperature of the flux is -30℃ to 30℃. Based on the mixed powder, the mass percentage content of the flux is ≥0.2wt%.

[0008] In Al-Si alloys, Cu and / or Zn are further introduced to form AlSiCu alloys or AlSiCuZn alloys. AlSi alloys include α-Al and Si phases, while AlSiCu alloys include α-Al, Si, and Al₂Cu phases. AlSiCuZn alloys also include Zn dissolved in solid solution. It is known that the overall melting point of AlSiCu or AlSiCuZn alloys is significantly lower than that of AlSi alloys, mainly due to the presence of the low-melting-point Al₂Cu phase and the low-melting-point element Zn. This allows for foaming at lower temperatures, reducing erosion of the upper and lower substrates and improving the strength of the foamed material. Therefore, the addition of low-melting-point Al-Cu microstructure can effectively lower the melting point of Al-Si alloys.

[0009] High-alloy AlSiCu or AlSiCuZn powders have high hardness, making it difficult to produce significant deformation during powder briquettes preparation and hot rolling. This results in low-quality products and a high scrap rate. Compared to pre-alloyed AlSiCu or AlSiCuZn powders, adding Cu and Zn in pure powder form improves the initial compaction density and uniformity of the powder briquettes. Furthermore, pure powders exhibit better plastic deformation coordination during hot rolling.

[0010] However, when Cu is added in pure powder form, it cannot alloy with AlSi powder under existing conventional processing techniques. This results in materials containing an appropriate amount of Cu, but failing to reach the ideal melting point and thus unable to foam at lower temperatures. Specifically, this manifests as the presence of undiffused Cu particles in the backscattered electron diffusion pattern. Unlike Cu, Zn does not exhibit this problem. Therefore, this invention is based on a foamed aluminum alloy system with Cu as a secondary alloying element, aiming to improve the foaming performance of mixed powders containing copper powder in foamed aluminum.

[0011] For the diffusion preparation of aluminum foam using powder metallurgy, directly preparing the foaming precursor by mixing powders does not allow Al to diffuse into Cu, but rather exists as pure Cu particles, failing to form a low-melting-point Al2Cu phase, and the melting is uneven, which is not conducive to the subsequent foaming process.

[0012] This invention utilizes the chemical activity of flux during hot rolling (when the flux is near the solidus temperature, extrusion and friction can physically enhance its interfacial contact and oxide film peeling ability, thereby "activating" its potential chemical activity (locally destroying the film structure through solid-phase reaction with adjacent powders). Although the oxide film on the powder surface has not reached the solidus temperature, diffusion alloying can still be achieved. The core is that the oxide film is not an absolute barrier: it has micro-cracks, pinholes, thermal stress cracking, and other microscopic defects, providing natural diffusion channels for atoms. At high temperatures, the oxide film physically softens (e.g., Al2O3 transforms into a viscoelastic state) and its chemical activity increases, further reducing diffusion resistance. Ultimately, Al and Cu atoms diffuse through the "incomplete film" and defect channels, completing alloying). This breaks down the dense oxide film on the Cu powder surface, promoting the directional diffusion of Al elements into the Cu powder matrix, thereby forming a diffusion layer mainly composed of intermetallic compounds in situ inside the Cu powder. The melting point of this diffusion layer is significantly lower than that of Al-Si alloys, thus enabling rapid melting in subsequent foaming processes, providing key thermodynamic conditions for the uniform nucleation and stable growth of the foam structure.

[0013] The flux content is too low, resulting in incomplete diffusion, which leads to low porosity and uneven foaming.

[0014] For example, the difference between the solidus temperature and the hot rolling temperature of the flux is -30℃ to 30℃, such as -30℃, -28℃, -27℃, -25℃, -22℃, -20℃, -18℃, -15℃, -12℃, -10℃, -5℃, 0℃, 2℃, 5℃, 8℃, 10℃, 12℃, 15℃, 18℃, 20℃, 25℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] For example, based on the mixed powder, the flux has a mass percentage content of ≥0.2wt%, such as 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, or 0.9wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the solidus temperature of the flux is 450~550℃, for example, it can be 450℃, 462℃, 473℃, 484℃, 495℃, 506℃, 517℃, 528℃, 539℃ or 550℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] The temperature of hot rolling is constrained by the base material, so it cannot be increased or decreased indefinitely. The solidus temperature of the flux should be considered in relation to the hot rolling temperature. If the solidus temperature of the flux is too high, its activity cannot be activated.

[0018] Preferably, the flux includes potassium fluoroaluminate flux and / or cesium fluoroaluminate flux.

[0019] Both types of fluxes are low-corrosion fluoroaluminates. Their mechanism of action is as follows: During the hot rolling process (480-520℃), they selectively destroy the CuO / Cu2O oxide film on the surface of Cu powder through chemical activity (CuO melting point 1235℃, Cu2O melting point 1230℃). Simultaneously, they undergo interfacial reactions with Al and Zn, driving Al and Zn atoms to diffuse into the Cu powder matrix, ultimately forming a "diffusion layer" on the surface of the Cu powder. The main components of this diffusion layer are Al2Cu, Al-Cu solid solution, or Al-Zn-Cu solid solution. The melting point of this diffusion layer is significantly lower than that of pure Cu (1083℃), while the melting point of the diffusion layer can be reduced to 532-580℃. This allows it to melt synchronously with the AlSi10 matrix during the subsequent foaming stage, providing a liquid channel for bubble nucleation.

[0020] Preferably, based on the mixed powder, the flux content is 0.2~0.7wt%, for example, it can be 0.2wt%, 0.26wt%, 0.32wt%, 0.37wt%, 0.43wt%, 0.48wt%, 0.54wt%, 0.59wt%, 0.65wt%, or 0.7wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] An appropriate amount of flux will be used entirely or mostly for film breaking during hot rolling, leaving only a small portion in the foamed preform, which has little impact on foaming. When the flux content is too high, the excessive flux forms continuous channels or layered networks in the material, becoming the preferred escape path for the decomposition gas of the foaming agent, resulting in the inability to form cells. When the flux content is too low, the diffusion is incomplete, resulting in low porosity and uneven foaming.

[0022] Preferably, based on the matrix material, the matrix material comprises 75-93 wt% AlSi. 10The powder can be, for example, 75wt%, 77wt%, 79wt%, 81wt%, 83wt%, 85wt%, 87wt%, 89wt%, 91wt%, or 93wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0023] AlSi10 powder is preferred because it has good flowability compared to other powders, which is beneficial for mold filling and uniformity of briquettes, moderate plasticity, and coordinated deformation during hot rolling.

[0024] Preferably, the matrix material is based on 7 to 20 wt% Cu powder, for example, it can be 7 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] Preferably, the matrix material is based on 0 to 10 wt% Zn powder, for example, it can be 0 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] It is known that when Cu and / or Zn are further introduced into Al-Si alloys, the overall melting point of the resulting AlSiCu alloy or AlSiCuZn alloy is significantly lower than that of AlSi alloy.

[0027] As a known technique, a high Cu powder content results in the mixed powder composition exceeding the eutectic point, forming a hypereutectic structure and producing coarse primary phases, while simultaneously increasing the melting point. Conversely, a low Cu powder content fails to effectively lower the system's melting point. The Cu powder content must be controlled appropriately to effectively reduce the aluminum alloy's melting point; otherwise, foaming at lower temperatures is difficult, resulting in low porosity and poor uniformity in low-temperature foaming. High-temperature foaming exacerbates the erosion of both the upper and lower substrates.

[0028] As a known technique, to further lower the melting point of aluminum alloys, Zn can be added. Experimental studies have shown that adding Zn in pure powder form is also more suitable. However, with an exemplary Zn powder content of 0-10 wt%, the Zn content is too high, and the composition of the mixed powder exceeds the eutectic point, forming a hypereutectic structure and producing coarse primary phases. Simultaneously, the melting point begins to increase, which is actually detrimental to foaming.

[0029] Preferably, the foaming agent comprises TiH2 powder.

[0030] Preferably, based on the mixed powder, the mass percentage of the foaming agent is 0.3~1.2wt%, for example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, or 1.2wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] TiH2 undergoes a decomposition reaction when heated to 400-600℃ (TiH2→Ti+H2↑), generating high-purity hydrogen gas (H2) in situ. Bubbles nucleate and grow within the molten metal, ultimately forming a porous structure. The amount of TiH2 added directly affects the bubble density and pore size distribution: too low a content (<0.3%) results in insufficient bubble quantity and low porosity. Too high a content (>1.2%) may lead to excessive bubble aggregation, forming large-sized defect pores.

[0032] In a second aspect, the present invention provides a method for preparing the mixed powder for foamed aluminum as described in the first aspect, the preparation method comprising the following steps: The matrix raw materials, foaming agent and flux are mixed evenly using a powder mixer to obtain a mixed powder for foamed aluminum.

[0033] Preferably, the mixing speed of the powder mixer is 50~100 r / min, for example, it can be 50 r / min, 56 r / min, 62 r / min, 67 r / min, 73 r / min, 78 r / min, 84 r / min, 89 r / min, 95 r / min or 100 r / min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The mixing time is 30~120 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Low rotation speed (<50 rpm) may result in insufficient dispersion of powder agglomerates, while high rotation speed can easily cause severe friction and heat generation between powder particles or between powder particles and the mixing tank, which can exacerbate powder oxidation.

[0035] Short-term mixing (<30 min) cannot achieve uniform dispersion of AlSi10, Cu, Zn, and functional additives (flux, TiH2). Long-term mixing (>120 min) can improve uniformity, but may lead to accelerated oxidation of the powder surface.

[0036] Thirdly, the present invention provides a foamed aluminum composite material, the foamed aluminum composite material comprising a first substrate, a foamed aluminum layer and a second substrate stacked sequentially.

[0037] The foamed aluminum layer is formed by foaming the mixed powder of foamed aluminum described in the first aspect.

[0038] Preferably, the porosity of the aluminum foam layer is 40% to 78%, for example, it can be 40%, 45%, 49%, 53%, 57%, 62%, 66%, 70%, 74% or 78%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the first substrate and the second substrate are each made of 1xxx series aluminum alloy, 3xxx series aluminum alloy or 6xxx series aluminum alloy.

[0040] Fourthly, the present invention provides a method for preparing the aluminum foam composite material described in the third aspect, the method comprising: (1) Foamed aluminum is mixed powder and cold-pressed into blocks by a tablet press.

[0041] (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform.

[0042] (3) The hot-rolled preform is hot-rolled to obtain a foamed preform. The difference between the hot-rolling temperature and the solidus temperature of the flux is -30℃ to 30℃.

[0043] (4) The foamed preform is foamed to obtain the foamed aluminum composite material.

[0044] Specifically, the geometry of the limiting groove matches the pressure block so that the pressure block is fully embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after embedding is flush with the surface of the first substrate.

[0045] When the flux is near its solidus temperature, extrusion and friction can enhance its interfacial contact and oxide film peeling ability through physical action, thereby "activating" its potential chemical activity. If the temperature is too low, the flux is a rigid solid and cannot be activated, ions cannot migrate, the oxide film hinders diffusion, alloying stagnates, and the powder has poor plasticity, making it prone to cracking due to large deformation, resulting in limited density improvement. If the temperature is too high, the powder is severely oxidized, the oxide film thickens, and TiH2 decomposes prematurely to produce hydrogen gas, forming pores and reducing density. Furthermore, in the later foaming stage, the premature decomposition of some TiH2 leads to insufficient gas production, reducing the porosity of the aluminum foam.

[0046] For example, the difference between the hot rolling temperature and the solidus temperature of the flux is -30℃ to 30℃, such as -30℃, -28℃, -27℃, -25℃, -22℃, -20℃, -18℃, -15℃, -12℃, -10℃, -8℃, -5℃, 0℃, 2℃, 5℃, 8℃, 10℃, 12℃, 15℃, 18℃, 20℃, 22℃, 25℃, 28℃ or 30℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the deformation amount of the hot rolling is 65-80%, for example, it can be 65%, 67%, 69%, 70%, 72%, 74%, 75%, 77%, 79% or 80%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Mechanical compression of pores and reshaping of particle morphology directly affect density and the number of diffusion channels. Increased deformation expands the particle contact area, increases grain boundary and dislocation density at the interface, and allows flux to penetrate along the microcracks created by deformation, further opening diffusion channels. When the deformation is too small (<65%), the density is insufficient, physically isolating diffusion. However, when the deformation is too large (>80%), the already alloyed powder, due to the excessively high content of alloying elements, undergoes work hardening (excessively high dislocation density), resulting in cracks or delamination. During foaming, these cracks provide channels for gas escape, leading to uneven foaming and reduced porosity.

[0049] Preferably, the hot rolling temperature is 480~520℃, for example, it can be 480℃, 485℃, 489℃, 494℃, 498℃, 503℃, 507℃, 512℃, 516℃ or 520℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the cold pressing pressure is ≥300MPa, for example, it can be 300MPa, 306MPa, 312MPa, 317MPa, 323MPa, 328MPa, 334MPa, 339MPa, 345MPa or 350MPa, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Insufficient pressure results in insufficient contact area between particles, weak mechanical interlocking, and a significant reduction in the macroscopic strength of the compact. Even slight external force can cause it to break, failing to meet the basic requirements for subsequent processing.

[0052] Preferably, the foaming temperature is 600~750℃, for example, it can be 600℃, 617℃, 634℃, 650℃, 667℃, 684℃, 700℃, 717℃, 734℃ or 750℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] If the foaming temperature is too low, the foaming agent decomposes slowly or incompletely, resulting in insufficient gas generation and ineffective material expansion. Furthermore, the high viscosity of the foaming matrix reduces fluidity, easily leading to uneven foaming. If the foaming temperature is too high, it accelerates the decomposition of the foaming agent, causing a large release of gas in a short period. If the gas generation rate exceeds the viscosity increase rate of the material, bubbles are prone to merging and rupture, forming large or interconnected pores, or even localized collapse. The final product exhibits poor cell uniformity and low closed-cell ratio, resulting in excessively low density.

[0054] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The mixed powder for foamed aluminum provided by the present invention contains flux, and the solidus temperature of the flux is close to that of the hot rolling temperature, which can break the dense oxide film on the surface of Cu powder, so that Al and / or Zn elements diffuse into the interior of Cu powder in a directional manner, forming a diffusion layer mainly composed of Al and Zn solid solution or intermetallic compound in situ inside Cu powder. The melting point of the diffusion layer is significantly lower than that of pure Cu, so that it can be rapidly melted in the subsequent foaming process and can be directly foamed without annealing. (2) The porosity of the aluminum foam composite material provided by the present invention can be controlled within a reasonable range, the foaming is uniform, and the production efficiency is significantly improved. Attached Figure Description

[0055] Figure 1 This is a backscattered electron image of the hot-rolled foamed preform in Embodiment 1 of the present invention.

[0056] Figure 2 This is a backscattered electron image of the hot-rolled foamed preform in Comparative Example 1 of this invention.

[0057] Figure 3 This is a backscattered electron image of the hot-rolled foamed preform in Comparative Example 5 of this invention. Detailed Implementation

[0058] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0059] As a specific embodiment of the present invention, a mixed powder for foamed aluminum is provided, the mixed powder comprising a matrix material, a foaming agent, and a flux. Based on the matrix material, the matrix material comprises 75-93 wt% AlSi. 10The mixture comprises 7-20 wt% Cu powder and 0-10 wt% Zn powder. The flux includes potassium fluoroaluminate flux and / or cesium fluoroaluminate flux; the solidus temperature of the flux is 507-550°C, and the mass percentage of the flux is 0.2-0.7 wt% based on the mixed powder. The foaming agent includes TiH2 powder; the mass percentage of the foaming agent is 0.3-1.2 wt% based on the mixed powder.

[0060] As a specific embodiment of the present invention, a method for preparing the above-mentioned mixed powder for foamed aluminum is provided. The preparation method includes: using a powder mixer to mix the matrix raw material, foaming agent and flux evenly, the powder mixer speed is 50~100 r / min, the mixing time is 30~120 min, and the mixed powder for foamed aluminum is obtained.

[0061] In another specific embodiment of the present invention, a foamed aluminum composite material is provided, comprising a first substrate, a foamed aluminum layer, and a second substrate stacked sequentially; the foamed aluminum layer is formed by foaming with the aforementioned mixed powder for foaming aluminum. The thickness of the foamed aluminum layer is 60-90%. The first substrate is made of 1xxx series aluminum alloy, 3xxx series aluminum alloy, or 6xxx series aluminum alloy, and its thickness is 5-20%. The second substrate is made of 1xxx series aluminum alloy, 3xxx series aluminum alloy, or 6xxx series aluminum alloy, and its thickness is 5-20%. In another specific embodiment of the present invention, a method for preparing the above-mentioned foamed aluminum composite material is provided, the method comprising the following steps: (1) Foamed aluminum is made by cold pressing mixed powder into tablets using a tablet press. The pressure of cold pressing is ≥300MPa, and the tablets are pressed into blocks. (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform; specifically, the geometry of the limiting groove is matched with the pressure block so that the pressure block is completely embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after being embedded is flush with the surface of the first substrate.

[0062] (3) The hot-rolled preform is hot-rolled, the deformation of the hot-rolled preform is 65~80%, the hot-rolling temperature is 480~520℃, and the difference between the hot-rolling temperature and the solidus temperature of the flux is -30℃~30℃, to produce the foamed preform. (4) The foamed preform is foamed at 600~750℃ to obtain the foamed aluminum composite material.

[0063] Foamed aluminum mixed powder Foamed aluminum composite powder A1: comprises a matrix material, a foaming agent, and a flux. Based on the matrix material, the matrix material comprises 82 wt% AlSi.10 The mixture comprises 13 wt% Cu powder and 5 wt% Zn powder. The flux consists of 92% KAlF4-8% CsAlF4 flux (parts by weight, the same below), with a flux content of 0.2 wt% based on the mixed powder; the solidus temperature of the flux is 507°C. The foaming agent is TiH2 powder; with the foaming agent content of 0.5 wt% based on the mixed powder.

[0064] The preparation method of the above-mentioned mixed powder for foamed aluminum includes: using a powder mixer to mix the matrix raw material, foaming agent and flux evenly, the powder mixer speed is 80 r / min, the mixing time is 60 min, and the mixed powder for foamed aluminum is obtained.

[0065] Foamed aluminum mixed powder A2: comprises a matrix material, a foaming agent, and a flux. Based on the matrix material, the matrix material comprises 75 wt% AlSi. 10 The mixture comprises 15 wt% Cu powder and 10 wt% Zn powder. The flux includes KAlF4 flux, with a mass percentage content of 0.5 wt% based on the mixed powder; the solidus temperature of the flux is 550°C. The foaming agent is TiH2 powder; with a mass percentage content of 0.3 wt% based on the mixed powder.

[0066] The preparation method of the above-mentioned mixed powder for foamed aluminum includes: using a powder mixer to mix the matrix raw material, foaming agent and flux evenly, the powder mixer speed is 100 r / min, the mixing time is 30 min, and the mixed powder for foamed aluminum is obtained.

[0067] Foamed aluminum composite powder A3: comprises a matrix material, a foaming agent, and a flux. Based on the matrix material, the matrix material comprises 93 wt% AlSi. 10 The flux is 7 wt% Cu powder. The flux comprises 80% KAlF4-20% CsAlF4 flux, with a mass percentage content of 0.3 wt% based on the mixed powder; the solidus temperature of the flux is 490°C. The foaming agent is TiH2 powder; with a mass percentage content of 1.2 wt% based on the mixed powder.

[0068] The preparation method of the above-mentioned mixed powder for foamed aluminum includes: using a powder mixer to mix the matrix raw material, foaming agent and flux evenly, the powder mixer speed is 50 r / min, the mixing time is 120 min, and the mixed powder for foamed aluminum is obtained.

[0069] Foamed aluminum composite powder A4: comprises a matrix material, a foaming agent, and a flux. Based on the matrix material, the matrix material comprises 78 wt% AlSi. 10The mixture comprises 20 wt% Cu powder and 2 wt% Zn powder. The flux includes CsAlF4 flux, with a mass percentage content of 0.7 wt% based on the mixed powder; the solidus temperature of the flux is 450°C. The foaming agent is TiH2 powder; with a mass percentage content of 0.7 wt% based on the mixed powder.

[0070] The preparation method of the above-mentioned mixed powder for foamed aluminum includes: using a powder mixer to mix the matrix raw material, foaming agent and flux evenly, the powder mixer speed is 60 r / min, the mixing time is 100 min, and the mixed powder for foamed aluminum is obtained.

[0071] Foamed aluminum mixed powder A5: The only difference between it and foamed aluminum mixed powder A1 is that, based on the mixed powder, the flux content is 0.8 wt%, and the rest is the same as foamed aluminum mixed powder A1, which will not be repeated here.

[0072] A6, a mixed powder for foamed aluminum, differs from A3 only in that, based on the matrix material, the matrix material comprises 95 wt% AlSi. 10 The powder contains 5 wt% Cu powder, and the rest is the same as the mixed powder A3 for foamed aluminum, so it will not be described again here.

[0073] Mixed powder D1 for foamed aluminum: The only difference between D1 and A1 for foamed aluminum is that the mixed powder does not contain flux. All other aspects are the same as those for A1 for foamed aluminum, and will not be repeated here.

[0074] Mixed powder D2 for foamed aluminum: The only difference between D2 and mixed powder A1 for foamed aluminum is that the flux in the mixed powder is replaced by CsAlF4 flux instead of 92%KAlF4-8%CsAlF4 flux. All other aspects are the same as those in mixed powder A1 for foamed aluminum, and will not be described in detail here.

[0075] Mixed powder D3 for foamed aluminum: The only difference between D3 and mixed powder A1 for foamed aluminum is that the flux in the mixed powder is replaced by KAlF4 flux instead of 92%KAlF4-8%CsAlF4 flux. All other aspects are the same as those in mixed powder A1 for foamed aluminum, and will not be described again here.

[0076] The only difference between foamed aluminum mixed powder D4 and foamed aluminum mixed powder A1 is that, based on the mixed powder, the flux content is 0.1 wt%, and the rest are the same as foamed aluminum mixed powder A1, which will not be repeated here.

[0077] Example 1 This embodiment provides a foamed aluminum composite material, comprising a first substrate, a foamed aluminum layer, and a second substrate stacked sequentially; the foamed aluminum layer is formed by foaming with Al mixed powder for foaming aluminum, and its thickness accounts for 75%. The first substrate is made of AA1050 aluminum alloy, and its thickness accounts for 12.5%. The second substrate is also made of AA1050 aluminum alloy, and its thickness accounts for 12.5%.

[0078] This embodiment also provides a method for preparing the above-mentioned aluminum foam composite material, the method comprising the following steps: (1) Foamed aluminum is mixed powder and cold-pressed into blocks by a tablet press. The cold pressing pressure is 320 MPa. (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform; specifically, the geometry of the limiting groove is matched with the pressure block so that the pressure block is completely embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after being embedded is flush with the surface of the first substrate.

[0079] (3) The hot-rolled preform is hot-rolled with a deformation of 75% and a temperature of 500°C. The difference between the hot-rolling temperature and the solidus temperature of the flux is -7°C (calculated by subtracting the solidus temperature of the flux from the hot-rolling temperature) to form the foamed preform. (4) The foamed preform is foamed at 700°C to obtain the foamed aluminum composite material.

[0080] Example 2 This embodiment provides a foamed aluminum composite material, comprising a first substrate, a foamed aluminum layer, and a second substrate stacked sequentially; the foamed aluminum layer is formed by foaming with A2 mixed powder for foaming aluminum, and its thickness accounts for 90%. The first substrate is made of AA3003 aluminum alloy, and its thickness accounts for 5%. The second substrate is also made of AA3003 aluminum alloy, and its thickness accounts for 5%.

[0081] This embodiment also provides a method for preparing the above-mentioned aluminum foam composite material, the method comprising the following steps: (1) Foamed aluminum is mixed powder and cold-pressed into blocks by a tablet press. The cold pressing pressure is 310 MPa. (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform; specifically, the geometry of the limiting groove is matched with the pressure block so that the pressure block is completely embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after being embedded is flush with the surface of the first substrate.

[0082] (3) The hot-rolled preform is hot-rolled with a deformation of 80% and a temperature of 520°C. The difference between the hot-rolled temperature and the solidus temperature of the flux is -30°C (calculated by subtracting the solidus temperature of the flux from the hot-rolled temperature) to form the foamed preform. (4) The foamed preform is foamed at 750°C to obtain the foamed aluminum composite material.

[0083] Example 3 This embodiment provides a foamed aluminum composite material, comprising a first substrate, a foamed aluminum layer, and a second substrate stacked sequentially; the foamed aluminum layer is formed by foaming with A3 mixed powder for foaming aluminum, and its thickness accounts for 68%. The first substrate is made of AA6061 aluminum alloy, and its thickness accounts for 16%. The second substrate is also made of AA6061 aluminum alloy, and its thickness accounts for 16%.

[0084] This embodiment also provides a method for preparing the above-mentioned aluminum foam composite material, the method comprising the following steps: (1) Foamed aluminum is mixed powder and cold-pressed into tablets by a tablet press. The cold pressing pressure is 300 MPa to obtain compressed blocks; (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform; specifically, the geometry of the limiting groove is matched with the pressure block so that the pressure block is completely embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after being embedded is flush with the surface of the first substrate.

[0085] (3) The hot-rolled preform is hot-rolled with a deformation of 65% and a temperature of 510°C. The difference between the hot-rolled temperature and the solidus temperature of the flux is 20°C (calculated by subtracting the solidus temperature of the flux from the hot-rolled temperature) to form the foamed preform. (4) The foamed preform is foamed at 650°C to obtain the foamed aluminum composite material.

[0086] Example 4 This embodiment provides a foamed aluminum composite material, comprising a first substrate, a foamed aluminum layer, and a second substrate stacked sequentially; the foamed aluminum layer is formed by foaming with A4 mixed powder for foaming aluminum, and its thickness accounts for 60%. The first substrate is made of AA3003 aluminum alloy, and its thickness accounts for 20%. The second substrate is also made of AA3003 aluminum alloy, and its thickness accounts for 20%.

[0087] This embodiment also provides a method for preparing the above-mentioned aluminum foam composite material, the method comprising the following steps: (1) Foamed aluminum is mixed powder and cold-pressed into blocks by a tablet press. The cold pressing pressure is 330 MPa. (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform; specifically, the geometry of the limiting groove is matched with the pressure block so that the pressure block is completely embedded in the limiting groove, and the depth of the limiting groove is the same as the thickness of the pressure block so that the surface of the pressure block after being embedded is flush with the surface of the first substrate.

[0088] (3) The hot-rolled preform is hot-rolled with a deformation of 70% and a temperature of 480°C. The difference between the hot-rolled temperature and the solidus temperature of the flux is 30°C (calculated by subtracting the solidus temperature of the flux from the hot-rolled temperature) to form the foamed preform. (4) The foamed preform is foamed at 600°C to obtain the foamed aluminum composite material.

[0089] Example 5 This embodiment provides a foamed aluminum composite material, which differs from Embodiment 1 only in that the foamed aluminum layer is formed by foaming with a mixed powder A5 for foaming aluminum. All other aspects are the same as in Embodiment 1 and will not be repeated here.

[0090] Example 6 This embodiment provides a foamed aluminum composite material, which differs from Embodiment 3 only in that the foamed aluminum layer is formed by foaming with a mixed powder A6 for foaming aluminum, and the foaming temperature is adjusted to 800°C. All other aspects are the same as in Embodiment 3, and will not be repeated here.

[0091] Example 7 This embodiment provides a foamed aluminum composite material, which differs from Embodiment 3 only in that the foamed aluminum layer is formed by foaming with a mixed powder A6 for foaming aluminum. All other aspects are the same as in Embodiment 3 and will not be repeated here.

[0092] Example 8 This embodiment provides a foamed aluminum composite material, which differs from Embodiment 1 only in that the deformation amount of hot rolling is 85%, and the rest is the same as Embodiment 1, and will not be repeated here.

[0093] Comparative Example 1 This comparative example provides a foamed aluminum composite material, which differs from Example 1 only in that the foamed aluminum layer is formed by foaming with a mixed powder D1 for foaming aluminum. All other aspects are the same as in Example 1 and will not be repeated here.

[0094] Comparative Example 2 This comparative example provides a foamed aluminum composite material, which differs from Example 1 only in that the foamed aluminum layer is formed by foaming with a mixed powder D2 for foamed aluminum, that is, the difference between the hot rolling temperature and the solidus temperature of the flux is 50°C (measured by subtracting the solidus temperature of the flux from the hot rolling temperature). All other aspects are the same as in Example 1, and will not be repeated here.

[0095] Comparative Example 3 This comparative example provides a foamed aluminum composite material, which differs from Example 1 only in that the foamed aluminum layer is formed by foaming with a mixed powder D3 for foamed aluminum, that is, the difference between the hot rolling temperature and the solidus temperature of the flux is -50℃ (measured by subtracting the solidus temperature of the flux from the hot rolling temperature). All other aspects are the same as in Example 1, and will not be repeated here.

[0096] Comparative Example 4 This comparative example provides a foamed aluminum composite material, which differs from Example 1 only in that the foamed aluminum layer is formed by foaming with a mixed powder D4 for foaming aluminum. All other aspects are the same as in Example 1 and will not be repeated here.

[0097] Comparative Example 5 This comparative example provides a foamed aluminum composite material, which differs from Example 1 only in that the deformation amount of hot rolling is 60%, and the rest is the same as Example 1, and will not be repeated here.

[0098] Detection method: Determination of complete copper powder diffusion: The presence of undiffused Cu was determined by using backscattered electron microscopy (BSEM) diffusion maps. Taking Example 1, Comparative Example 1, and Comparative Example 5 as examples, the BSEM images of the foamed preforms obtained after hot rolling are shown below. Figures 1-3 As shown, from Figures 1-3 It can be seen that in Example 1, after hot rolling, Al diffuses into the interior of Cu particles to form an alloy compound, while in Comparative Example 1 and Comparative Example 5, Cu powder still exists in the form of pure Cu particles.

[0099] Solidus temperature: The melting temperature of the sample was characterized using a NETZSCH STA 449C model synchronous thermal analyzer. An inert atmosphere (such as Ar) was used, and the heating rate was 10 K / min. The solidus was labeled using the NETZSCH Proteus Themal Analysis 8.0.3 software that comes with the instrument.

[0100] Porosity of aluminum foam layer: CT scan of the foamed sample along the thickness direction is performed, and a planar image of the thickness center is selected. The area ratio of the foam cells is calculated using ZEN core, which is the porosity.

[0101] Pore ​​uniformity of aluminum foam layer: The pore uniformity of aluminum foam layer is defined as the difference between the maximum pore diameter and the average pore diameter. Generally, a pore uniformity of ≤3mm is considered to be uniform.

[0102] Erosion depth: Prepare a cross-sectional metallographic image of the foamed sample and use an optical microscope to photograph the interface between the substrate layer and the foam layer. There will be a clear boundary. The original thickness of the substrate minus the thinnest point is the erosion depth.

[0103] The detection results of the above embodiments and comparative examples are shown in Table 1.

[0104] Table 1 The following points can be observed from Table 1: (1) As can be seen from Examples 1-4, the mixed powder for foamed aluminum provided by the present invention contains flux, and the difference between the solidus temperature and the hot rolling temperature of the flux is controlled at -30℃ to 30℃. The chemical activity of the flux during the hot rolling process can break the dense oxide film on the surface of Cu powder, promoting the directional diffusion of Al elements or Al and Zn elements into the Cu powder matrix, thereby forming a diffusion layer mainly composed of Al and Zn solid solutions or intermetallic compounds in situ inside the Cu powder. The melting point of this diffusion layer is significantly lower than that of Al-Si alloy or pure Cu (because the addition of Al and Zn lowers the liquidus temperature of the system), so that rapid melting can be achieved in the subsequent foaming process, providing key thermodynamic conditions for the uniform nucleation and stable growth of the foam structure. Therefore, for foamed aluminum alloy systems with Cu as the secondary alloying element, foaming can be achieved without long-term annealing, significantly shortening the production cycle and reducing energy consumption. Moreover, the porosity of the aluminum foam layer obtained by the present invention is between 53% and 78%, the pore uniformity of the aluminum foam layer is ≤3mm, the pores are uniform, and the erosion depth of the substrate is ≤100μm, indicating low erosion.

[0105] (2) The effect of flux (2.1) Amount of flux added An appropriate amount of flux will be used entirely or mostly for film breaking during hot rolling, leaving only a small portion in the foamed preform, which has little impact on foaming. Comparing Example 1 with Comparative Examples 1 and 4, it can be seen that when the flux content is too low, the diffusion is incomplete, resulting in low porosity and uneven foaming. Comparing Example 1 with Example 5, it can be seen that when the flux content is too high, the excess flux forms continuous channels or layered networks in the material, becoming the preferred escape path for the decomposition gas of the foaming agent, resulting in the inability to form cells.

[0106] (2.2) Temperature difference between the solidus temperature of the flux and the temperature of hot rolling Comparing Example 1 and Comparative Examples 2-3, it can be seen that the temperature difference between the solidus temperature of the flux and the hot rolling temperature in Comparative Examples 2-3 is too large. In Comparative Example 2, the solidus temperature of the flux is much lower than the hot rolling temperature, resulting in incomplete copper powder diffusion, low foaming porosity, and uneven foaming. In Comparative Example 3, the solidus temperature of the flux is much higher than the hot rolling temperature. The flux is a rigid solid and cannot be activated, ions cannot migrate, the oxide film hinders diffusion, alloying stagnates, resulting in poor foaming uniformity and foaming effect. This indicates that maintaining the temperature difference between the solidus temperature of the flux and the hot rolling temperature within a reasonable range, and the flux being close to the solidus temperature during hot rolling, allows extrusion and friction to enhance its interfacial contact and oxide film peeling ability through physical action, thereby "stimulating" its potential chemical activity and promoting alloying.

[0107] (3) Effect of copper powder content As is known, a high Cu powder content results in the mixed powder composition exceeding the eutectic point, forming a hypereutectic structure and producing coarse primary phases, while simultaneously increasing the melting point. Conversely, a low Cu powder content makes foaming difficult at lower temperatures. Experiments demonstrate that the Cu powder content should be controlled appropriately to effectively lower the melting point of the aluminum alloy; otherwise, foaming at lower temperatures is difficult (see the comparison between Examples 3 and 7). Specifically, low-temperature foaming results in low porosity and poor uniformity, while high-temperature foaming exacerbates the erosion of the upper and lower substrates (see the comparison between Examples 3 and 6).

[0108] (4) Influence of deformation during hot rolling When the deformation is too small (<65%), the density is insufficient, causing diffusion to be physically isolated (see comparison of Example 1 and Comparative Example 5); however, when the deformation is too large (>80%), the alloyed powder, due to the excessive content of alloying elements, undergoes work hardening (excessive dislocation density), resulting in cracks or delamination. During the foaming process, these cracks provide channels for gas escape, leading to uneven foaming and reduced porosity (see comparison of Example 1 and Example 8). This indicates that the present invention preferably controls the deformation of hot rolling within a reasonable range, which can better achieve uniform foaming without annealing and results in high foam porosity.

[0109] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A mixed powder for foamed aluminum, characterized in that, The mixed powder comprises a matrix material, a foaming agent, and a flux; the matrix material comprises aluminum, silicon, and copper. The copper element exists in the form of copper powder; The difference between the solidus temperature and the hot rolling temperature of the flux is -30℃ to 30℃; based on the mixed powder, the mass percentage content of the flux is ≥0.2wt%.

2. The mixed powder for foamed aluminum according to claim 1, characterized in that, The solidus temperature of the flux is 450~550℃.

3. The mixed powder for foamed aluminum according to claim 1 or 2, characterized in that, The flux includes potassium fluoroaluminate flux and / or cesium fluoroaluminate flux.

4. The mixed powder for foamed aluminum according to any one of claims 1 to 3, characterized in that, Based on the mixed powder, the flux content is 0.2~0.7wt%.

5. The mixed powder for foamed aluminum according to any one of claims 1 to 4, characterized in that, Based on the matrix material, the matrix material comprises 75-93 wt% AlSi 10 pink; Preferably, based on the matrix raw material, the matrix raw material includes 7-20 wt% Cu powder; Preferably, the matrix raw material is based on 0-10 wt% Zn powder.

6. A foamed aluminum composite material, characterized in that, The aluminum foam composite material includes a first substrate, an aluminum foam layer, and a second substrate stacked sequentially. The foamed aluminum layer is formed by foaming with a mixed powder of foamed aluminum as described in any one of claims 1 to 5.

7. A method for preparing the aluminum foam composite material according to claim 6, characterized in that, The preparation method includes: (1) Foamed aluminum is mixed powder and cold-pressed into blocks by a tablet press; (2) A pressure block is embedded in the limiting groove of the first substrate with a limiting groove, and then a second substrate is covered on the pressure block to obtain a hot-rolled preform. (3) The hot-rolled preform is hot-rolled to obtain a foamed preform; the difference between the hot-rolling temperature and the solidus temperature of the flux is -30℃ to 30℃. (4) The foamed preform is foamed to obtain the foamed aluminum composite material.

8. The preparation method according to claim 7, characterized in that, The deformation amount of the hot rolling is 65-80%.

9. The preparation method according to claim 7 or 8, characterized in that, The hot rolling temperature is 480~520℃.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The foaming temperature is 600~750℃.

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